Snow on the Desert Road is making driving conditions hazardous and police are advising motorists in affected parts of the central North Island to delay non-urgent travel.
Police say if you have to travel, take extra care - slow down, make sure your lights are on, extend following distances and allow extra time for your journey.
There's a similar warning in the South Island where Southland, Otago and the alpine passes have had snowfalls and freezing temperatures in the past 24 hours with potentially more overnight.
The New Zealand Transport Agency says wet and icy road conditions are likely in many areas of the southern South Island on Thursday morning.
Drivers in places like inland Southland need to be ready for black ice particularly at daybreak, said NZTA senior journey manager Neil Walker.
"Please slow down if you are driving on these highways in the early morning. Ice-prone highways will be gritted but snow or rain and freezing temperatures can still make them dangerous," he said.
Black ice is largely invisible on the road surface and is commonest in shady areas and on bridges - early morning and late at night, Mr Walker said.
Drivers on State Highway 94 to and from Milford Sound are required by law to carry chains from 5pm tonight between Te Anau Downs and Milford Sound.
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